Hi
Mysoulishome,
The books listed are wonderful resources for you to suggest to your step mom. There are a few others listed in the link NaughtyNibbler posted that may be helpful as well.
A book that is one of the classics is
I Hate You, Don't Leave Me. The 2010 edition is revised and updated. I've not read through the entire book yet, but it was one of the very first books written about BPD back in 1989.
It is wonderful that you are extending a hand of understanding and kindness to her, and how amazing that she is aware!
Sounds as if you've been a good source of information yourself.
Wools